I try to provide the most useful advice that I can to anyone that is interested in writing. I usually do that because I am hoping to get advice in return. I'm certainly no expert, so anyone asking me for help can no doubt help me as well. If there is one piece of advice I find myself giving out often it is that well-developed characters can make the difference between a bad story and an amazing story. The actual story can be a little lukewarm, but great, well-developed characters can make it something that people will remember.
One of my classes has to put up with me trying to teach them some creative writing skills, and the first thing that I do is stress the importance of characters. Part of the multi-day lesson is showing them a character profile that ask questions like the character's name, age, greatest strength, greatest weakness, etc. I tell them that when they write, they should be able to fill out a character profile for all of their major characters in order to make them more three-dimensional and believable. I make them fill out a character profile on themselves as practice. Once we have done that, I show them a few minutes of a movie that most of them are familiar with and have them all do a profile on the same character. We were doing this particular exercise and I noticed a problem- a significant number of my students did not answer (or did not seriously answer) the question in the profile about where the character was from. The movie never said it specifically, but there were hints dropped and characteristics that should have given it away. Those hints and characteristics were not caught by all, and in desperation to complete the assignment several students wrote next to the category "Birthplace" answers like "a hospital," "Planet Earth," and the every puzzling "IDK." I required students to give different answers to these questions. I could hear them mumbling to themselves a question that I asked myself after class was finished. Does it really matter where a character was born?
It is remarkably easy when writing to go overboard with the details. Some professional authors are masters at being detailed to such an amazing degree that you can see, hear, and taste everything going on in their books. These detail masters are rare. Most writers that begin going into great detail eventually bore their readers. Is it too much detail to mention the birthplace of all of the major characters? I'm sure that my students think so, and I don't blame them at all. I don't blame them because they are right. If a writer goes into great depth about all of the details of every major character's life, hopes, and dreams, their book would be the size of an encyclopedia set and no one would likely read past the introduction of the first character.
So why did I make these students redo their answers? Because it is still important. I would never expect a story to contain all of the details in the character profile within its writings. The character profile isn't for the reader. The character profile is for the writer. Whenever you are writing a story, your characters need to be as real to you as the people in your life. You don't need to know the details of their lives so that you can write about their lives. You need to know the details of their lives so that your character will have the same actions, reactions, logic, illogic, passion, and apathy of real people. If you don't know and love (or love to hate) your characters, how can you expect your readers to?
Does it matter where a character comes from? I suppose that depends. If you believe that the characters in a story can make the difference between mediocre and exceptional writing as I do, then yes you need to know where the characters are from, as well as a great many other details about them. If you think that the characters are just there as part of the story, then don't worry about where they are from. I'll probably still read your work, but I'll probably only do it once.